As is known, railway beacons (also known by the French term “balise”) are installed along railway lines, receive an electromagnetic enabling signal from a vehicle travelling along the railway line, and generate in response a coded response signal (telegram) transmitted to the vehicle and containing information relative to the location and travel of the vehicle.
For example, the information may indicate the presence of an obstacle along a section of the railway line downstream from the beacon location.
Beacons comprise a receiving antenna and a transmitting antenna, and are normally laid between the rails of the railway line and anchored to the sleepers.
Data coding and transmission devices (known as “encoders) are also installed along railway lines to acquire in-field information concerning the status of the railway line, and to transmit an appropriate telegram, selected on the basis of the input signals, to the beacons.
The input signals to the encoder normally come from relay contacts located along the railway line, and which are switched by predetermined events, such as red-to-green switching of a traffic light, point operation, etc.
In other words, the beacons simply provide for relaying telegrams selected and transmitted by the encoders to vehicles travelling along the railway line.
It is therefore essential that the telegrams transmitted to vehicles travelling along a given section of railway line, and on which the safety of the vehicles depends, be fully reliable.
The encoder must therefore ensure a negligible degree of error in both telegram selection on the basis of railway line status, and in selected telegram transmission to the beacons.